In principle, widely varying types of hybrid architectures of a drive train of a motor vehicle are known which combine an internal combustion engine and an electric motor to ensure an efficient drive of the motor vehicle. In general, three different levels of hybridization are distinguished which differ in relation to the contribution of drive torque supplied by the electric motor.
For so-called micro-hybrid vehicles, usually an electric motor is provided for an automatic start-stop system and a braking energy recovery system to charge a comparatively small starter battery. The electric motor is not used to drive the vehicle.
In so-called mild hybrids, the electric motor in contrast supports the internal combustion engine to increase the power. Also with a suitable design of the drive train, the energy occurring during a braking process can be partly recovered in a generator mode of the electric motor.
In contrast to the hybridization stages described above, full hybrid vehicles are able to be driven completely by the electric motor. In such vehicles for example it can be provided that the internal combustion engine merely drives an electric generator which supplies the electric motor with the electrical energy and/or charges a battery. Therefore smaller-dimensioned internal combustion engines can be used than in motor vehicles with comparable performance levels. In addition the internal combustion engine can be operated in an efficient operating state as power peaks can normally be covered by extracting energy from the battery.
Hybrid architectures are known in which an electric motor and an internal combustion engine are connected together or with the drive train via one or two clutches. A disadvantage, in particular in architectures with two clutches, is the complex design of the clutches and the functional and geometric integration of the electric motor in the drive train. Also control of the system is comparatively complex.